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DNA and RNA

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DNA (Deoxyribonucleic Acid) is the genetic material found inside cells responsible for a living organism's development and function. Most of the DNA is found in the nucleus and is organised into structures called chromosomes. RNA (Ribonucleic Acid) is a nucleic acid that is in all living cells that is structurally similar to DNA. RNAs cause biological reactions, control gene expression and sense and communicate responses to cellular signals. The general rule of molecular biology is that DNA makes RNA makes protein. DNA and RNA along with proteins make up the three major macromolecules that are essential for life.

DNA

DNA (deoxyribonucleic acid) is a molecule which contains the unique genetic code of each living organism. DNA is made up of two strands that are arranged in a double helix which resembles a twisted ladder. The two strands are made up of alternating sugar (deoxyribose) and phosphates. Attached to each sugar are four nucleotide bases:

  • Adenine (Pairs with thymine)
  • Cytosine (Pairs with guanine)
  • Guanine (Pairs with cytosine)
  • Thymine (Pairs with adenine)

These bases contain the genetic code which specifies the sequence of the amino acids within proteins. The human genome consists of 3.2 billion bases of DNA. DNA contains instructions for the synthesis of proteins and other molecules.

The division of cells is important for cells to multiply and organisms to grow. DNA replication has to occur in order for the genetic material to be transmitted to the progeny of any organism or cell. When a cell divides, it must duplicate the DNA in its genome so that the daughter cells (the result of a dividing parent cell) have the same generic material as their parent cell.

DNA’s structure provides a simple solution for DNA replication. The two strands are separated by and then DNA polymerase (an enzyme) recreates each strand’s DNA sequence.

RNA

RNA (Ribonucleic Acid) is a nucleic acid that is present in all living cells. Like DNA, RNA is made up of nucleotides and are one of the macromolecules that are essential for living organisms. RNA is one of the most crucial parts of a cell’s regulatory players and they catalyse biological reactions, control and moderate gene expression and sensing and communicating responses to cellular signals. RNA also carries the genetic information for many viruses.

The structure of RNA is very similar to DNA: each nucleotide has a nucleobase (cyclic compound), a ribose sugar and a phosphate group. However, RNA molecules are single-stranded and can have very complex 3D structures. Like DNA, RNA has four nucleotide bases, three of them being the same as DNA: adenine, guanine and cytosine. However, instead of thymine, RNA’s fourth base is uracil.

The three types of RNA are:

  • Messenger RNA (mRNAs): One of the best-known structures of RNA are known as messenger RNAs (mRNAs). MRNAs copy and transport the genetic material that directs the synthesis of proteins by the ribosomes. MRNAs are present in all cellular organisms.
  • Transfer RNA (tRNA): Responsible for bringing basic protein building blocks (amino acids) to the protein factories in response to the coded instructions that have been introduced by mRNAs. This protein-building process is known as translation.
  • Ribosomal RNA (rRNA): A part of the ribosome factory which makes protein production possible.

Differences Between DNA and RNA

Function

DNA: DNA stores and replicates genetic material. It is responsible for the storing and reading of genetic material that is found in all living organisms.

RNA: RNA transforms the genetic material contained in the DNA to a format that is used to build proteins. Those proteins are then moved to ribosomal protein factories.

Structure

DNA: DNA is made up of two strands that are in the shape of a double helix. Both strands consist of nucleotides and each of these nucleotides contains a phosphate, a 5-carbon sugar molecule and a nitrogenous base.

RNA: RNA consists of one strand that is shorter than DNA, but is also made up of nucleotides. They have complex three dimensional structures.

Length

DNA: DNA is much logner than RNA. For example, chromosomes are a single, long DNA molecule that are several centimetres long when unravelled.

RNA: The length of RNA molecules change but are generally much shorter than DNA molecules.

Sugar

DNA: The five-carbon sugar found in DNA is deoxyribose which helps to form the backbone of DNA molecules. It contains one less hydroxyl (an oxygen atom that is bonded to a hydrogen atom).

RNA: RNA contains ribose sugar molecules without the hydroxyl modifications that are found in deoxyribose.

Bases

DNA: The four nucleotide bases found in DNA are adenine (A), thymine (T), guanine (G) and cytosine (C).

RNA: Rna shares the same three bases as DNA (adenine, thymine and guanine) but its fourth base is uracil.

Location

DNA: DNA is found in the nucleus and a small amount can also be found in the mitochondria.

RNA: RNA can be found in the nucleolus and then travels to specialised parts of the cytoplasm depending on the type of RNA formed.

Reactivity

DNA: DNA is a more stable molecule than RNA thanks to its deoxyribose sugar.

However, DNA is more vulnerable to damage by ultraviolet light.

RNA: Since ribose sugar is found in RNA, it is more reactive than DNA and is not stable in an alkaline environment.

But RNA is more resistant to damage than DNA when it comes to ultraviolet light.